There is a storage apparatus that causes its host computer to identify a virtual volume (logical volume), and allocates storage resources from a storage pool to the logical volume when needed. The storage device releases an area that is no longer needed, and returns its storage resources to the storage pool.
In this way, the storage apparatus effectively uses the resources therein.
Meanwhile, an offload data transfer function has been disclosed. The offload data transfer function is for offloading tasks, such as copying and moving files, from a host computer to a storage apparatus, and thereby reducing the central processing unit (CPU) load of the host computer and the communication load between the host computer and the storage apparatus (see, for example, Japanese Laid-open Patent Publications No. 2008-130080 and No. 2011-76572).
If an area release is accepted during execution of the offload data transfer function, the storage apparatus might lose data to be transferred by the offload data transfer. To prevent such data loss, the storage apparatus needs to save data to a saving volume from the area to be released.
However, saving data to the saving volume consumes significant time and memory resources, and therefore is an inefficient solution.